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27 
28 #ifndef UPB_MESSAGE_EXTENSION_INTERNAL_H_
29 #define UPB_MESSAGE_EXTENSION_INTERNAL_H_
30 
31 #include "upb/base/descriptor_constants.h"
32 #include "upb/base/string_view.h"
33 #include "upb/mem/arena.h"
34 #include "upb/message/message.h"
35 #include "upb/mini_table/extension_internal.h"
36 
37 // Must be last.
38 #include "upb/port/def.inc"
39 
40 // The internal representation of an extension is self-describing: it contains
41 // enough information that we can serialize it to binary format without needing
42 // to look it up in a upb_ExtensionRegistry.
43 //
44 // This representation allocates 16 bytes to data on 64-bit platforms.
45 // This is rather wasteful for scalars (in the extreme case of bool,
46 // it wastes 15 bytes). We accept this because we expect messages to be
47 // the most common extension type.
48 typedef struct {
49   const upb_MiniTableExtension* ext;
50   union {
51     upb_StringView str;
52     void* ptr;
53     char scalar_data[8];
54   } data;
55 } upb_Message_Extension;
56 
57 #ifdef __cplusplus
58 extern "C" {
59 #endif
60 
61 // Adds the given extension data to the given message.
62 // |ext| is copied into the message instance.
63 // This logically replaces any previously-added extension with this number.
64 upb_Message_Extension* _upb_Message_GetOrCreateExtension(
65     upb_Message* msg, const upb_MiniTableExtension* ext, upb_Arena* arena);
66 
67 // Returns an array of extensions for this message.
68 // Note: the array is ordered in reverse relative to the order of creation.
69 const upb_Message_Extension* _upb_Message_Getexts(const upb_Message* msg,
70                                                   size_t* count);
71 
72 // Returns an extension for the given field number, or NULL if no extension
73 // exists for this field number.
74 const upb_Message_Extension* _upb_Message_Getext(
75     const upb_Message* msg, const upb_MiniTableExtension* ext);
76 
77 #ifdef __cplusplus
78 } /* extern "C" */
79 #endif
80 
81 #include "upb/port/undef.inc"
82 
83 #endif /* UPB_MESSAGE_EXTENSION_INTERNAL_H_ */
84